Sound arrester in the ventilator of sound-arresting rooms



b- 1946. M. TOMINAGA 2,394,342

SOUND ARRESTER IN THE VENTILATOR OF SOUND-ARRESTING ROOMS Filed July 15, 194

INVENTOR Patented Feb. 5, 1946 SOUND ARRESTER IN THE VENTILATOR OF SOUND-ARRESTING ROOIVIS Masaichi Tominaga, Kamata-ku, Tokyo, Japan; vested in theAlien Property Custodian Application July 15, 1941, Serial No. 402,549 In Japan August 5, 1940 2 Claims.

This invention relates 'to a soundearresting structure consisting in the feature that the inner surface of the cylindrical ventilator in the "sound generating room is all covered with a sound-arresting material, having, on the inner surface of the upper portion of the ventilator, a female screw shaped sound-absorbing wall projected inwardly, so as to eliminate sound waves in advancing them spirally.

The object of the present invention is to manufacture economically a sound-absorbing apparatus which completely prevents sounds from flow ng outside the room.

The present invention is, with object of removing the foregoing defects, provided, on the roof or flank of the sound generating room, with one or more cylindrical ventilators each having, on the inner surface, a spirally disposed and inwardly projecting sound-absorbing wall whereby the ventilating cylinder is not only reinforced but the absorption of sounds and the escape of the air current are favorably increased.

The construction of the invention is illustrated in the accompanying drawing, in which:

Fig. 1 is a vertical cross-section of a sound generating room provided with the sound-absorbing apparatus according to the present in vention partly showing a sectional elevation along a l ne CC of Fig. 2.

Fig. 2 is a horizontal section taken on line A-A of Fig. 1.

Fig. 3 is a horizontal section taken on line B-B of Fig. 1.

Fi 4 is a vertical cross-section taken on line E-E of Fig. 5 in case two paralleled spiral walls are provided.

Fig. 5 is a detail horizontal cross-section taken on line DD of Fig. 4.

These figures illustrate the present invention by two examples. As regards the sound-arrester at the mouth of ventilator shown in Figs. 1, 2 and 3, there are provided at the four corners of the sound-arresting room 6 in which such noisy sound generators as machinery, engine, propeller for trial or talkie filming projector is held the cylindrical ventilators 2 erected on the floor and passing through the roof, each ventilator being cut away, in its inner part facing the room 6, to provide an air-inducing opening 3. All over the inner surface of the said ventilating cylinder, a sound-absorbing plate or lining 2 is pasted, and, the upper part of the cylinder 1. e. the part above the ceiling of the room, is provided, on its inner wall, with a female screw shaped sound-absorbing wall 4 projecting inwardly a distance substantially equal to about a third the diameter of the cylinder. Such sound absorbing material may beCelotex, which is compressed bagasse, kapok orlayers of cotton or burlap. The length of the said screw shaped sound-absorbing -wal1 is limited to one or, if necessary, to two or three convolutions. If the pitch of the screw shaped wall is steep, the vent lation is good, because the number of the wall convolutions is small, but chances of repeated sound absorptions reduce. If the pitch is gentle, the absorption of sounds is complete, but as the number of convolutions or flights increases the ventilation is obstructed proportionally. The pitch and number of flights in the said screw shaped sound-absorbing wall. therefore depend on the strength of the sounds coming from the sound generator.

A sound, observation booth 5 is built at the mid dle of the sound-arresting room 6, and, around the booth 5, is placed a sound generator the sounds generated therefrom being observed by the observers in the booth 5.

As one of the modifications of the presentinvention, shown in Figs. 4 and 5, a central core on column 1 having on its c rcumference a male screw shaped sound-absorbing wall 8 with the same pitch as that of the abovementioned female screw shaped Wall 4 is set up coaxially in the said female screw shaped sound-absorbing wall 4. .In this embodiment, since two spiral soundabsorbing walls are disposed in the vent lating cylinder, the effect on arresting sounds is far better than the case when a single wall is used.

According to the foregoing construction, sound waves coming from the sound generator in the sound-arresting room 6 are induced to the airinducing opening 3 directly or after reflection from the wall, door and ceiling of the sound-arresting room 6. and the sounds of short wavelength are partly absorbed and eliminated by the sound-absorbing wall 2' in the cylinder. The remaining sounds first collide with the lowest flight of the screw or spiral shaped wall 4, and thereafter, repeated reflection between the flights facing each other, causes the sounds to be continuously absorbed and completely eliminated.

The sounds of long wave-length which are difficult of elimination effect various reflections in several directions between the flights of the spiral walls and create sufficient phasic differences among the sound-waves, in consequence of which the sounds are eliminated completely after their mutual interferences.

In the present invention, the passage of various sounds of long and short wave-length is, as

abovementioned, spirally extended in order to efiect complete sound-eliminating operations by especially complicating the reflection of the sounds in the said spiral passage, and, in addition thereto, it is free from obstruction to ventilation, and hence the present invention can be used more effectively than those hitherto used.

In case the entrance of the ventilator is formed in the side-wall of the sound-arresting room, the ventilating cylinder having the foregoing screw shaped sound-absorbing wall on the inner wall may be disposed horizontally. The ventilating cylinder having similar spiral wall may also be constructed on the ceiling instead of on the floor. The use of sound current regulators at the entrance of the ventilating cylinder makes the present invention more effective. The number and diameter of the said ventilating cylinder depend upon the area of the sound-arresting room and kinds of Sounders.

I claim:

1. A sound-arresting structure for preventing the emanation of sounds from the ventilator of sound-arresting room having a cylindrical ventilator whose inner surface is covered with a 25 sound-arresting material. a female screw shaped sound-absorbing wall projected inwardly on the inner surface at the upper portion of the said cylindrical ventilator, and a column having a male screw shaped sound-absorbing wall with the same pitch as that of the said female screw shaped wall and set up coaxially within the latter wall so that these two spiral walls are alternately disposed in the ventilating cylinder the outer faces of the turns of the male screw extending outwardly so that their outer faces are substantially in alinement with the inner faces of the female turns and the turns of the male screw are located between the turns of the female screw.

2. In a structure of the character described, walls forming a cornered room, and shaped at the corners to form cylindrical ventilating shafts. communicating with the interior of the room at the bottom and with the outside air at the top, the inner wall of said shaft being formed with a female screw, a male screw in said shaft with turns lying between the turns of the female screw and extending outward so as to cut off any direct passage through the shaft.

MASAICHI TOMINAGA. 

